Atmos. Chem. Phys. Discuss., 13, 1399-1433, 2013
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Continuous monitoring of summer surface water vapour isotopic composition above the Greenland Ice Sheet
H. C. Steen-Larsen1,2, S. J. Johnsen1, V. Masson-Delmotte3, B. Stenni4, C. Risi5, H. Sodemann6, D. Balslev-Clausen1, T. Blunier1, D. Dahl-Jensen1, M. D. Ellehøj1, S. Falourd3, V. Gkinis1, A. Grindsted1, J. Jouzel3, T. Popp1, S. Sheldon1, S. B. Simonsen1,7, J. Sjolte1, J. P. Steffensen1, P. Sperlich1, A. E. Sveinbjörnsdóttir8, B. M. Vinther1, and J. W. C. White9
1Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Denmark
2Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, USA
3Laboratoire des Sciences du Climat et de l'Environnement, UMR CEA-CNRS-UVSQ/IPSL 8212, Gif-sur-Yvette, France
4Department of Mathematics and Geosciences, Environmental and Marine Sciences, University of Trieste, Italy
5Laboratoire de Météorologie Dynamique, Jussieu, Paris, France
6ETH, Institute for Atmospheric and Climate Science, ETH Zürich, Switzerland
7Danish Climate Center, DMI, Lyngbyvejen 100, 2100 Copenhagen, Denmark
8Science Institute, University of Reykjavik, Dunhaga 3, Reykjavik 107, Iceland
9Institute of Arctic and Alpine Research, Campus Box 450, University of Colorado, Boulder, CO 80309, USA

Abstract. We present here surface water vapor isotopic measurements conducted from June to August~2010 at the NEEM camp, NW-Greenland (77.45° N 51.05° W, 2484 m a.s.l.). Measurements were conducted at 9 different heights from 0.1 m to 13.5 m above the snow surface using two different types of cavity-enhanced near infrared absorption spectroscopy analyzers. For each instrument specific protocols were developed for calibration and drift corrections. The inter-comparison of corrected results from different instruments reveals excellent reproducibility, stability, and precision with a standard deviation of ~ 0.23‰ for δ18O and ~ 1.4‰ for δD. Diurnal and intra-seasonal variations show strong relationships between changes in local surface humidity and water vapor isotopic composition, and with local and synoptic weather conditions. This variability probably results from the interplay between local moisture fluxes, linked with firn-air exchanges, boundary layer dynamics, and large-scale moisture advection. Particularly remarkable are several episodes characterized by high (> 40‰) surface water vapor deuterium excess. Air mass back-trajectory calculations from atmospheric analyses and water tagging in the LMDZiso atmospheric model reveal that these events are associated with predominant Arctic air mass origin. The analysis suggests that high deuterium excess levels are a result of strong kinetic fractionation during evaporation at the sea ice margin.

Citation: Steen-Larsen, H. C., Johnsen, S. J., Masson-Delmotte, V., Stenni, B., Risi, C., Sodemann, H., Balslev-Clausen, D., Blunier, T., Dahl-Jensen, D., Ellehøj, M. D., Falourd, S., Gkinis, V., Grindsted, A., Jouzel, J., Popp, T., Sheldon, S., Simonsen, S. B., Sjolte, J., Steffensen, J. P., Sperlich, P., Sveinbjörnsdóttir, A. E., Vinther, B. M., and White, J. W. C.: Continuous monitoring of summer surface water vapour isotopic composition above the Greenland Ice Sheet, Atmos. Chem. Phys. Discuss., 13, 1399-1433, doi:10.5194/acpd-13-1399-2013, 2013.
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